Table 2.

Differential table for splanchnic arteriovenous malformations (AVMs)

Entity	General features	Computed Tomography	Magnetic Resonance Imaging	Ultrasound
Arteriovenous Malformation	Serpentine and hypertrophied feeding arteries, central nidus with tangled vessels, and early enhancement of enlarged draining veins. Can occur in any vascular territory.	NECT: Nonspecific soft tissue attenuation of mass. Multiphasic CECT: Angiographic phase: Hypertrophied serpentine feeding arteries, central nidus with tangled vessels, and early filling of enlarged draining veins. Venous Phase: Equilibration of enhancement of arteries and veins.	Noncontrast T1-GRE: High signal may represent hemorrhage, intravascular thrombosis, or flow related enhancement. Multiphasic T1-GRE +C: Same enhancement pattern as multiphasic CECT. T2WI: Flow voids.	Grayscale: Feeding arteries and draining veins seem as multiple anechoic spaces with echogenic nidus. Color Doppler: Intense flow with aliasing and apparent flow reversals. Spectral Doppler: High velocity, low resistance arterial waveforms. Pulsatile high velocity venous waveforms. Differentiation between arterial and venous waveforms is difficult.
Venous malformation	Most are located in the skin and subcutaneous tissues, but also can be trans-spatial, involving muscle, bone, and abdominal viscera. Simple malformation with slow flow and an abnormal venous network.	NECT: Hypoattenuating or heterogeneous lesions. May demonstrate phleboliths and fatty components. Multiphasic CECT: Slow and peripheral contrast enhancement with gradual filling. No enlarged feeding arteries. Lesion drained by enlarged veins.	Heterogeneous, usually septated lesions. Phleboliths appear as signal voids on all sequences. Noncontrast T1-GRE: Heterogeneous with high signal thrombosis or hemorrhage. Hemorrhagic or proteinaceous contents seen as fluid-fluid levels. Multiphasic T1-GRE +C: Same enhancement pattern as multiphasic CECT. T2WI: Lesions with large vascular channels are hyperintense and septated. Lesions with smaller vascular channels appear more solid with intermediate signal intensity.	Grayscale: Hypoechoic or heterogeneous in 80%. Anechoic channels in less than 50%. Sometimes, there is isoechoic thickening of the subcutaneous tissues. Phleboliths are hyperechoic with posterior shadowing, but seen in less than 20% of cases. Color Doppler: No arterial flow. Venous flow may be augmented by compression with transducer. Spectral Doppler: Monophasic, low velocity flow.
Hypervascular Peritoneal Metastases	Peritoneal metastases of renal cell carcinoma, gastro-intestinal stromal tumors, and carcinoid are usually hypervascular. Best imaging tool is CECT.	Size of implants is variable from tiny nodules to invasive soft tissue masses along the peritoneal surface and reflections. NECT: Calcifications may be present with carcinoid metastases. Ascites often seen. Multiphasic CECT: Demonstrate marked enhancement. May have prominent arterial feeding vessels and draining veins. May demonstrate central necrosis.	Noncontrast T1-GRE: Peritoneal soft tissue masses with variable signal intensity. Multiphasic T1-GRE +C: Marked enhancement. May demonstrate central necrosis. T2WI: Peritoneal thickening and soft tissue nodules usually intermediate signal intensity.	Grayscale: Echogenicity is variable relative to surrounding tissues. Color Doppler: Hypervascular. Spectral Doppler: May have high velocity low resistance waveform from arteriovenous shunting.
Pelvic Solitary Fibrous Tumor (SFT)	Well-defined soft tissue mass. Large range of sizes (1–25 cm) with most common sizes 5–8 cm.	NECT: Well-defined mass with heterogeneous attenuation. May contain central necrosis, cystic change, or hemorrhage. Calcifications rare. CECT: Well-defined hyperenhancing mass of variable uniformity.	Noncontrast T1-GRE: Iso- to hypointense. May demonstrate hyperintense hemorrhage. Multiphasic TI-GRE + C: Intense arterial enhancement. Multiple tubular flow voids due to large vessels. Persistent delayed enhancement due to fibrosis. T2WI: Heterogeneous signal intensity depends on cellular content. Multiple tubular flow voids due to vascular channels.	Grayscale: Well-defined mass with mixed echogenicity Doppler: Internal blood flow.
Extraadrenal Pheochromocytoma	Well-defined hypervascular mass in the extra-peritoneal pelvis along the course of common iliac vessels. MIBG scintigraphy localizes adrenal pheochromocytoma and extraadrenal paraganglioma.	NECT: Hypo- or isodense. Cystic or necrotic areas. May demonstrate hyperdense hemorrhage. Calcifications in 10%. Multiphasic CECT: May have homogeneous or heterogeneous enhancement with avid enhancement of solid parts.	Noncontrast T1-GRE: Heterogeneous signal intensity due to variable necrosis and/or hemorrhage. Multiphasic T1-GRE +C: Intense arterial enhancement with “salt and pepper” pattern. T2WI: Very high signal intensity.	Grayscale: Round circumscribed mass may be solid, cystic or both. Cyst fluid is anechoic or has echogenic debris with posterior acoustic enhancement. Acute hemorrhage is echogenic.
Mesenteric trauma with hemorrhage	Mesenteric infiltration. Extravasation of IV contrast. If bowel involved, wall thickening may be seen.	NECT: Variable appearance depending on amount of hemorrhage. Can range from mesenteric stranding or hyperdense hematoma to large volume hyperdense hemoperitoneum. “Sentinel clot sign” is highest point of attenuation at site of bleeding (>60 HU). If bowel involved, wall is thickened and possibly hyperdense. Multiphasic CECT: Active arterial extravasation seen as progressively enhancing extravascular contrast blush that follows density of the blood pool. May see bleeding source as round pseudoaneurysm.	Not usually performed in setting of trauma. T1-GRE: Mesenteric hematoma or hemorrhagic ascites as high signal. T1-GRE +C: Active arterial extravasation has same pattern of contrast enhancement as on CECT. T2WI: Hemorrhage signal intensity variable. But usually low signal acutely.	Grayscale: Abdominal and pelvic free fluid of variable echogenicity. May demonstrate anechoic pseudoaneurysm. Color Doppler: “Yin-yang” appearance of pseudoaneurysmal sac.